The invention relates to an X-ray detector comprising an X-ray detection element and a detection device which is responsive to fluorescent radiation generated in the X-ray detection element.
In a known detector of this kind, described in U.S. Pat. No. 3,866,047, the X-ray detection element is formed by monocrystals of, for example, thallium-activated sodium iodide. These X-ray detection crystals have the drawback of excessive afterglow for given applications, notably when measurements are performed with a comparatively high degree of repetition. It has also been proposed to utilize a monocrystal of bismuth germanate as the X-ray detection crystal. Bismuth germanate is known to have a comparatively short afterglow, but in comparison with said sodium iodide crystal it has the drawback that its efficiency is 10 to 25 times lower. For medical X-ray equipment such as, for example, a scanning X-ray examining apparatus, the low efficiency of the bismuth germanate X-ray detection element is unfavourable because the radiation dose required for the patient is then increased. If measurement with an acceptable dose is demanded, very severe requirements must be imposed as regards the electronic section of the detection device.